Pulper for paper stock



Nov, 11, 1952 w. K. KOLB ET AL 2,617,334

PULPER FOR PAPER STOCK Filed April 19, 1947 3 Sheets-Sheet 1 fnz/enzors: [50622,

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Patented Nov. 11, 1952 PULPER FOR PAPER. STOCK William K.. Kalb. and Samuel Wilson Pollock,

Appleton, Wisg assignors' to Valley Iron Works ComnanmAnnl s-,acormratmnQfW Sw cousin ApplicationAprillil, 1947, Serial No, 742,648

2 Claims; (01; 92-2-61) The present inventionrelatesto: a pulperfor paper stock.

In papermaking, a pulper is used to accomplish the preliminary breaking-up of pulp stocks or broke, so as to effect the mechanical separation and suspension of the fibers before they are put into the beater for intermediate or final refining. A pulper, in contrast to a beater, desirably accomplishes mere breaking-up or the mechanical separation of the cellul'osic fibers, while a beater besides separating the fibers, subjects them to a rubbing and shearing action. This rubbing and shearing action results in the production of hydrated or partially hydrated cellulosic fibers which may be of substantially equal lengths, and which tend to curl so as to form a paper having good felting qualities when deposited on the wire of the Fourdrinier papermaking machine.

The degree of hydration of the cellulosic fibers is very important in controlling the freeness of the final sheet. To obtain uniform hydration, it is desirable to effect the primary separation of the fibers rapidly in a pulper, which minimizes local hydration and results in fewer control difficulties in the beating step.

Heretofore, several types of pulpers have been devised, but, so far as we know, none has proven entirely satisfactory, due, itis believed, to the failure of these devices to provide means for positively controlling the circulation of the stock in the pulper, so as to effect rapid and uniform separation of the fibers. The provision of pulping apparatus wherein the circulation of the stock. is positively controlled during the pulping operation is, therefore, the principal object of the present invention. The pulper, of. the present invention is, in certain of its features, a modification of .the Seaborne beater which is fully described in U. S. Patents Nos. 1,691,308 and 2,129,789,'and during its operation produces a very uniform furnish, which is adapted. to be fed to a beater or other refining machine or, in some, instances, even directly to a papermaking machine. Other objects and advantages of the invention will be apparent by reference to the. following description and the accompanying drawings of one preferred embodiment of. the invention- In the. drawings:

Fig-1 is a side elevational view of a pulperembodying the features of my invention;

Fig. 2 is a sectional view. taken on line 2--2 of Fig. 1;

Fig. 3 is a sectional view taken on line 3-4 Fig. 2;

Fig.4 is a fragmentary, elevational' view, par: tially in section, showing a preferred method of; mounting knife blades on the rotor which con-.. stitutes a part of the apparatus illustrated in the other figures of the drawings; and

Fig. 5 is a fragmentary, plan view of the cover section of the pulper showing the pulp feeding opening.

The pulper illustrated in the drawings generally comprises a supporting frame, a large, closed container or tank, which is supported on the frame, rotor means for circulating and breaking up the pulp stock, and includes baffies and a feed screw means for positively controlling the recirculation of the pulp stock so as to insure numerous contacts of undisintegrated pulp with the rotor.

The supporting frame Iii includes a number of rigid structural mbers which are fastened together by welding, riveting, or the like. The frame I!) supports a closed tank or container 13, which is generally cylindrical in shape. The bot tom of the tank is is permanently closed by means of a metallic plate l5, as is the top by asimilar plate i? having a pulp charging opening i 9 which is desirably of large enough size to give access to the interior of the apparatus for cleaning and maintenance operations. The tank l3 may be made, as shown in the drawings, from fabricated steel sections 29 which are bolted to-- gether, or may be constructed from concrete, tile, castings, or any of the other materials that are commonly used in the paper art. The bottom corners of the tank are suitably well-rounded, as shown, in the drawings at 2!, so as to prevent excessive friction losses as the stock is circulated inthe tank.

A rotor 23, having a plurality of impeller blades 25 and pulping knife blades 21, is supported for free rotation, on a vertically extending shaft 29. The shaft 29 extends through a, suitable packing gland 3| at the base of the tank [3, and is sup-. ported at its lower end by a suitable thrust bearing 33 attached to the supporting frame In. The upper end of the shaft 29 is journaled in a suitable bearing 35 sup-ported upon an upper frame I I, above the cover ll of the tank 3. The upper end of the shaft 22 is extended so as to be operatively connected to a gear box 37!, which is adapted to be powered from a suitable source, such as the electric motor shown at 39.

The section of the shaft 29 which is intermediate the rotor 23 and the cover plate ll includes. a worm conveyor section, II, which adapted tov force material, upon rotation, downwardlyintov 3 contact with the rotor 23. The shaft may also be provided with a series of breaker bars 43 which, when the shaft 29 is rotated, tend to break up large masses of pul material. The breaker bars 43 may not conveniently be used with materials which contain an appreciable amount of string, wire, etc., as they present projections upon which such materials may wind.

The rotor 23 is of generally convex, platedisc shape, as is shown in the drawings. A plurality of impeller blades 25 are attached to the raised central portion of the rotor 23 by means of bolts 26 or other suitable connecting means. Four impeller blades 25 are illustrated, but any number may be used if they are evenly arranged so that a dynamically-balanced structure results. The impeller blades 25 are back-curved, as illustrated, to increase the radial thrust which is exerted on the paper stock, thus improving the positive recirculation. A plurality of pulping knife blades 21 are evenly placed around the periphery of the depressed portion of the rotor 23 so as to provide a balanced unit. The rotor 23 is of substantially smaller diameter than the outer tank I3.

A convenient method of mounting the knife blades 21 is shown in Figs. 3 and 4, where segments 28 having generally concentric arcuate edges and each containing a plurality of knives are attached to the rotor 23 by means of machine screws 45. This attaching means provides for easy removal of the segments 28 when sharpening and replacement is necessary. In order to insure a rigid knife structure, the inner edges of the segments 28 are machined, as shown in the drawings at 41, so as to be fitted into an undercut groove 49 which extends around the rotor structure. In order to increase the radial thrust on the stock, the knife blades 2? are backcurved in a manner similar to the impeller blades 25.

The baffle means, used to provide positive control of the recirculation of the paper stock, includes a vertically extending cylindrical baille r draft tube i, which is supported from the walls of the tank 53 by means of a plurality of director vanes or flow control baffles 53. The diameter of the cylindrical draft tube 5! is equal to, or slightly smaller than, the diameter of the rotor 23. The knife blades 21 which extend to the rim of the rotor 23 desirably extend slightly beyond the outer defining surface of the draft tube 5!; this is of some importance in obtaining the maximum possible flow rate of the material being pulped. The draft tube 5! may be fabricated from heavy, steel plate or suitable material and the sections are preferably joined on the inner side by reinforcing members 55 which serve an added function as abrading members. The bafiie cylinder 5! is supported in close proximity with the upper edge of the knife blades 2"! by the flow control vanes 53. The clearance between the knife blades 21 and the lower edge of the cylinder 5! may be adjustable; it is desirably set at about T 6- of an inch for ordinary krait pulp lap and kraft broke, when working at normal concentrations. lhe lower edge of the draft tube 5| is desirably smooth surfaced so as to minimize the hydration of the broken up pulp and to also reduce the shearing action in the area between the tube 5| and the pulping knives 21.

The flow control bafiies or vanes 53 are fabricated from suitable sheet steel, and are of relatively massive construction in order that they may be strong enough to support the draft tube .4 5|. It is desirable that the vanes 53 shall not have any projections which may impede the free circulation of the paper stock. In the illustrated apparatus, the baffles 53 are inclined about 30 to 45 degrees from the vertical, in the direction of rotation of the rotor 23. Maximum efficiency of the flow directing baffles 53 is interrelated with the concentration of the paper stock. Our investigations have shown that the less concentrated the furnish, the greater should be the variation of the angle from the vertical. However, under widely varying conditions, a thirty-degree inclined vane is a good average structure; but, if the machine is required to constantly pulp either extremely attenuated or extremely concentrated paper stocks, these conditions should be allowed for in the installation of the machine. Even vertical vanes can be used advantageously in certain instances, as where high furnish concentrations are encountered.

In order to facilitate quick dumping of the pulped stock, a quick acting valve is provided in the bottom of the tank, as is illustrated at 57. It is also desired that a suitable source of water be provided so that the tank may be rapidly charged on initial operation, and the concentration of the paper stock may be easily controlled. A vent pipe 59 should be provided to eliminate the possibility of an air look when rapidly dumping the stock.

In a particularly satisfactory embodiment of the invention, designed for pulping hard kraft stock in batches of 2,000 pounds at a concentration of 5.6 percent, the rotor has a diameter of '76 inches and is rotated in a tank 11 feet in diameter. The rotor carries 40 evenly spaced knives about 3 inches high, and the clearance between the top of the knives and the lower surface of the draft tube is about 1% of an inch. The worm conveyor in this machine has a diameter of about 16 inches and a length of '78 inches. The depth of the tank is approximately 96 inches, and the draft tube is '75 inches in diameter, and is positioned with its lower end about '7 inches from the bottom of the tank. The draft tube in this structure is supported by four flow directing vanes substantially as illustrated in the drawings.

During operation, the tank [3 is filled with water to the level of about the top of the cylindrical draft tube 5|. The drive motor 39 is energized and the rotor 23 is turned until a speed of about 100 R. P. M. is reached. Due to the pressure differential created by the rotor 23, the water within the draft tube 5i will drop and that in the annular space between the outer tank and the tube will tend to move slowly in the direction of rotation of the rotor structure 23. The water is guided, however, along an upward and somewhat spiral path by means of the flow control baffles 53 which are disposed so as to cause the rotating motion of the mass of liquid to be resolved into a vertical component which adds to the pressure diiferential created by the rotor.

The charge is dumped into the pulper through the charging opening iii in the top covering ll of the tank l3, and is carried by the flowing liquid into the cylindrical draft tube or baffle 5i. The bundles of pulp laps, etc. are forced onto the rotor 23 and also broken up by action of the vertical worm conveyor All and the breaker bars 43 if they are used. The impeller blades 25 force the material outwardly until it is engaged by the draft tube 5| and the knife blades 2'! which tear apart the large pieces until they are small enough to be forced through the space between the rapidly rotating knife blades 27. The resulting circulating eifect produced by the cooperating action of the draft tube and the flow directing bafiies 53, as previously described, causes the particles which have been broken up to rise with the liquid, to go over the top of the draft tube 5|, downwardly through the tube, and to again pass through the area of the rotor. The rotor thus acts both as a disintegrating means and as a pump.

In a trial installation of the previously described pulper, wherein the rotor was rotated at a speed of about 100 R. P. M., the hard pulp laps were fed into the tank at a rate of about 600 pounds per minute, without overloading the machine. The pulping operation to produce a 5.6 percent paper stock required only about 12 minutes at the same speed.

The worm conveyor aids materially in effecting the submergence of the larger, unpulped portions of the lap or other material which is charged into the apparatus, with resultant decrease in the time required to effect complete pulping. This is especially true when pulping at stock concentrations of about 5 percent or over, in which range most of the present pulpers become ineificient, apparently due to poor circulation of the paper stock. The breaker bars, when their use is possible, are also of value in increasing the efiiciency of operation of the pulper by decreasing the time required for complete pulping of the charge.

The features of the invention that are believed to be new are expressly set forth in the appended claims.

We claim:

1. In a machine for pulping paper stock, a tank, a vertically disposed, cylindrical draft tube, which is fabricated of rigid plate material and which has a smooth bottom edge, supported in a central position within said tank by means of a plurality of generally vertically extending, radially disposed, spaced-apart, plate members, which extend across the space between the tank and the draft tube, said plate members also serving as baffles for controlling the flow of material being pulped in said machine in the space between said draft tube and said tank, a disc-shaped rotor disposed within said tank and supported for rotation in a generally horizontal plane at the lower end of said draft tube, said rotor havin a plu- 6 rality of generally radially extending pulping knives supported on the upper surface thereof, said knives having inner portions aligned with the space enclosed by said tube and outer portions in position to cooperate with the bottom edge of said draft tube, and means for rotating said rotor.

2. In a machine for pulping paper stock, a tank,

a vertically extending, cylindrical draft tube, which is fabricated of rigid plate material and which has a smooth surface on the lower edge, supported centrally within said tank, a plurality of equally spaced, generally vertically extending flow control bafiles disposed in the space between said draft tube and said tank, a rotatably supported, vertically extending worm conveyor disposed within said draft tube, a rotor having a diameter greater than that of the draft tube, said rotor being supported within said tank for rotatable movement adjacent the bottom of said tank, said rotor having a plurality of back-curved, pulping knives supported in close proximity to the lower edge of said draft tube for cooperating therewith, and a plurality of back-curved impeller blades for cooperating with said worm conveyor, and means for rotating said rotor and said worm conveyor.

WILLIAM K. KOLB.

S. WILSON POLLOCK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 114,588 Morse et a1. May 9, 1871 144,557 Moore et al Nov. 11, 1873 492,239 Schulte Feb. 21, 1893 610,122 Cook Aug. 30, 1898 1,691,308 Seaborne Nov. 13, 1928 1,778,860 Lindenfelser Oct. 21, 1930 1,886,020 Hoyer Nov. 1, 1932 2,129,789 Seaborne Sept. 13, 1938 2,289,612 Wells July 14, 1942 FOREIGN PATENTS Number Country Date 28,829 Germany Sept. 23, 1884 517,728 France June 24, 1920 12,666 Australia of 1928 403.913 Great Britain Jan. 4, 1934 

